Methods and procedures for polar encoding and decoding with low latency

ABSTRACT

A polar code may be initially divided into multiple polar component codes where the features of these component codes, such as the number of component codes and the size of the component codes, are determined based on parameters such as the number of available timing units within a transmission interval, interleaving depth, and decoder capability. For each selected component code, the order of code bit generation and their indexes may be determined. The determined indexes may be assigned into different, unique groups according to the order of code bit generation. An interleaving operation may be configured and then executed according to the determined index grouping. In the transmission phase, the code bits may be transmitted based on the identified order of the bit generation in the component polar codes, such as the determined index grouping.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/798,208, filed Jan. 29, 2019, the contents of which are incorporatedherein by reference.

BACKGROUND

Polar codes are the first channel code type analytically proven to becapacity achieving. Polar codes show comparable performance toconventional LDPC code or turbo code with low or no error floor whenaided by the embedded CRC, particularly for small to medium blocklengths. Polar codes with successive cancellation decoding requiresrelatively low encoding and decoding complexities. However, the decodingcomplexity and latency may increase in proportion to the list-size whenthe CRC-aided list decoding is adopted as well as the block-length ofthe codeword. The complexity and latency increase becomes a centralissue particularly in medium to large block-lengths, and limits theadoption of polar codes for high throughput regime including 5G NR eMBBdata rates (˜20 Gbps) and above.

SUMMARY

A polar code may be initially divided into multiple polar componentcodes where the features of these component codes, such as the number ofcomponent codes and the size of the component codes, are determinedbased on parameters such as the number of available timing units withina transmission interval, interleaving depth, and decoder capability. Foreach selected component code, the order of code bit generation and theirindexes may be determined. The determined indexes may be assigned intodifferent, unique groups according to the order of code bit generation.An interleaving operation may be configured and then executed accordingto the determined index grouping. In the transmission phase, the codebits may be transmitted based on the identified order of the bitgeneration in the component polar codes, such as the determined indexgrouping. In the receiver, the decoder may start its decoding process ofthe received channel symbols utilizing the order of the transmissioninformation made available to itself a priori, and therefore thedecoding process may star before receiving all channel symbols.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings,wherein like reference numerals in the figures indicate like elements,and wherein:

FIG. 1A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 1A according to an embodiment;

FIG. 10 is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A according to an embodiment;

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A according to an embodiment;

FIG. 2 is a diagram that illustrates an example polar encoder with thecode word block-length N=8;

FIG. 3 is a diagram that illustrates an example of LLR message passingfor BP decoding;

FIG. 4 is a diagram that illustrates an example method for orderedtransmission of polar code;

FIG. 5 is four diagrams that illustrate an example of polar codedecomposition into four possible component polar codes;

FIG. 6 are three diagrams that illustrate sequential encoding steps andcoded bit generations at each timing step for a given component polarcode of length N′=8;

FIG. 7 is a flow chart that illustrates an example method of identifyinga code bit order based on component polar codes with length N′=2^(n′);

FIG. 8 is a diagram that illustrates an example of ordered grouping andgroup interleaving;

FIG. 9 is a flow chart that illustrates an example of a NR multiplexingchain modified with an interleaving step 904 inserted;

FIG. 10 is a diagram that illustrates an example of timing relation inearly start decoding;

FIG. 11 is a flow chart illustrating an example decoding procedure;

FIG. 12 is graph illustrating an example of a comparison of simulatedblock error performance between example procedures for conventional andearly start decoding;

FIG. 13 is graph illustrating an example of a comparison of simulatedtiming steps between example procedures for conventional and early startBP decoding; and

FIG. 14 is graph illustrating an example of is graph illustrating anexample of a comparison of simulated timing steps between exampleprocedures for conventional and early start LDPC-like BP decoding.

DETAILED DESCRIPTION

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S-OFDM),unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bankmulticarrier (FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network (CN) 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d, any of which maybe referred to as a station (STA), may be configured to transmit and/orreceive wireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a NodeB, an eNode B(eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as agNode B (gNB), a new radio (NR) NodeB, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, and the like. The base station 114 a and/or the base station 114b may be configured to transmit and/or receive wireless signals on oneor more carrier frequencies, which may be referred to as a cell (notshown). These frequencies may be in licensed spectrum, unlicensedspectrum, or a combination of licensed and unlicensed spectrum. A cellmay provide coverage for a wireless service to a specific geographicalarea that may be relatively fixed or that may change over time. The cellmay further be divided into cell sectors. For example, the cellassociated with the base station 114 a may be divided into threesectors. Thus, in one embodiment, the base station 114 a may includethree transceivers, i.e., one for each sector of the cell. In anembodiment, the base station 114 a may employ multiple-input multipleoutput (MIMO) technology and may utilize multiple transceivers for eachsector of the cell. For example, beamforming may be used to transmitand/or receive signals in desired spatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink(DL) Packet Access (HSDPA) and/or High-Speed Uplink (UL) Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using NR.

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., an eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106.

The RAN 104 may be in communication with the CN 106, which may be anytype of network configured to provide voice, data, applications, and/orvoice over internet protocol (VoIP) services to one or more of the WTRUs102 a, 102 b, 102 c, 102 d. The data may have varying quality of service(QoS) requirements, such as differing throughput requirements, latencyrequirements, error tolerance requirements, reliability requirements,data throughput requirements, mobility requirements, and the like. TheCN 106 may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the CN 106 may be in direct or indirectcommunication with other RANs that employ the same RAT as the RAN 104 ora different RAT. For example, in addition to being connected to the RAN104, which may be utilizing a NR radio technology, the CN 106 may alsobe in communication with another RAN (not shown) employing a GSM, UMTS,CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106 may also serve as a gateway for the WTRUs 102 a, 102 b, 102c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), anyother type of integrated circuit (IC), a state machine, and the like.The processor 118 may perform signal coding, data processing, powercontrol, input/output processing, and/or any other functionality thatenables the WTRU 102 to operate in a wireless environment. The processor118 may be coupled to the transceiver 120, which may be coupled to thetransmit/receive element 122. While FIG. 1B depicts the processor 118and the transceiver 120 as separate components, it will be appreciatedthat the processor 118 and the transceiver 120 may be integratedtogether in an electronic package or chip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors. The sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor, an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, ahumidity sensor and the like.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) and DL(e.g., for reception) may be concurrent and/or simultaneous. The fullduplex radio may include an interference management unit to reduce andor substantially eliminate self-interference via either hardware (e.g.,a choke) or signal processing via a processor (e.g., a separateprocessor (not shown) or via processor 118). In an embodiment, the WTRU102 may include a half-duplex radio for which transmission and receptionof some or all of the signals (e.g., associated with particularsubframes for either the UL (e.g., for transmission) or the DL (e.g.,for reception)).

FIG. 10 is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 10, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 10 may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (PGW) 166. While the foregoing elements are depicted as part ofthe CN 106, it will be appreciated that any of these elements may beowned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have access or an interface to a Distribution System(DS) or another type of wired/wireless network that carries traffic into and/or out of the BSS. Traffic to STAs that originates from outsidethe BSS may arrive through the AP and may be delivered to the STAs.Traffic originating from STAs to destinations outside the BSS may besent to the AP to be delivered to respective destinations. Trafficbetween STAs within the BSS may be sent through the AP, for example,where the source STA may send traffic to the AP and the AP may deliverthe traffic to the destination STA. The traffic between STAs within aBSS may be considered and/or referred to as peer-to-peer traffic. Thepeer-to-peer traffic may be sent between (e.g., directly between) thesource and destination STAs with a direct link setup (DLS). In certainrepresentative embodiments, the DLS may use an 802.11e DLS or an 802.11ztunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may nothave an AP, and the STAs (e.g., all of the STAs) within or using theIBSS may communicate directly with each other. The IBSS mode ofcommunication may sometimes be referred to herein as an “ad-hoc” mode ofcommunication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width. The primarychannel may be the operating channel of the BSS and may be used by theSTAs to establish a connection with the AP. In certain representativeembodiments, Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) may be implemented, for example in 802.11 systems. ForCSMA/CA, the STAs (e.g., every STA), including the AP, may sense theprimary channel. If the primary channel is sensed/detected and/ordetermined to be busy by a particular STA, the particular STA may backoff. One STA (e.g., only one station) may transmit at any given time ina given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications (MTC), such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode) transmitting to the AP, all available frequency bands may beconsidered busy even though a majority of the available frequency bandsremains idle.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 104 may also be in communication with theCN 106.

The RAN 104 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 104 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement MIMO technology. For example,gNBs 180 a, 108 b may utilize beamforming to transmit signals to and/orreceive signals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a,for example, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs 180 a, 180 b, 180 c may implement carrier aggregationtechnology. For example, the gNB 180 a may transmit multiple componentcarriers to the WTRU 102 a (not shown). A subset of these componentcarriers may be on unlicensed spectrum while the remaining componentcarriers may be on licensed spectrum. In an embodiment, the gNBs 180 a,180 b, 180 c may implement Coordinated Multi-Point (CoMP) technology.For example, WTRU 102 a may receive coordinated transmissions from gNB180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containing avarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, DC, interworking between NR andE-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184 b, routing of control plane information towards Access andMobility Management Function (AMF) 182 a, 182 b and the like. As shownin FIG. 1D, the gNBs 180 a, 180 b, 180 c may communicate with oneanother over an Xn interface.

The CN 106 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a,184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whilethe foregoing elements are depicted as part of the CN 106, it will beappreciated that any of these elements may be owned and/or operated byan entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 104 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different protocol data unit (PDU)sessions with different requirements), selecting a particular SMF 183 a,183 b, management of the registration area, termination of non-accessstratum (NAS) signaling, mobility management, and the like. Networkslicing may be used by the AMF 182 a, 182 b in order to customize CNsupport for WTRUs 102 a, 102 b, 102 c based on the types of servicesbeing utilized WTRUs 102 a, 102 b, 102 c. For example, different networkslices may be established for different use cases such as servicesrelying on ultra-reliable low latency (URLLC) access, services relyingon enhanced massive mobile broadband (eMBB) access, services for MTCaccess, and the like. The AMF 182 a, 182 b may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro,and/or non-3GPP access technologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN106 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 106 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating UE IP address,managing PDU sessions, controlling policy enforcement and QoS, providingDL data notifications, and the like. A PDU session type may be IP-based,non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 104 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering DL packets, providing mobility anchoring, and the like.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 106 and the PSTN 108. In addition, the CN 106may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a local DN185 a, 185 b through the UPF 184 a, 184 b via the N3 interface to theUPF 184 a, 184 b and an N6 interface between the UPF 184 a, 184 b andthe DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

For a given wireless communication system, such as those described andrelated to FIGS. 1A, 1B, 1C, and 1D, there may be low latencyapplications of wireless communication, such as Ultra-reliable and lowlatency communication (URLLC) that requires very low latency in thedecoding process. Polar codes may provide some of the besterror-correction performances along with superior energy efficiency(e.g., energy/bit) for a different range of code blocks. However, theconventional decoding algorithms used in Polar codes, such assuccessive-cancellation (SC), and successive-cancellation-list (SCL) maysuffer from large decoding latency due to the sequential characteristicof these decoding procedures. The inherent latency in these approachesmay result in additional end-to-end link-level latency, which may alsotranslate into reduced throughput. It follows then that theapplicability of Polar codes with SC based decoding algorithms forerror-correction in URLLC as well as high-throughput communications(e.g., data communications, such as eMBB) may be relatively limited.However, BP (belief propagation) based decoding is an inherentlyparallel procedure that has significantly lower decoding latency andhigher throughput potential compared with the sequential decodingcandidates. In one or more embodiments discussed herein, there areapproaches to resolve and improve upon different encoding and decodingmethods that may improve the latency performance of BP based decoding byintroducing procedures to enable early-start of these decodingtechniques.

Due to its superior performance in small block lengths, polar codes maybe used as the channel coding scheme in control channel forward errorcorrection (FEC) operations in NR. Polar code encoding is defined as thefollowing:

c ₁ ^(N) =u ₁ ^(N) G _(N)  Equation 1

The codeword vector of polar code c₁ ^(N) is generated by the product ofthe input vector u₁ ^(N) and generator matrix G_(N). The polar code c₁^(N) and the input vector u₁ ^(N) may be binary vectors with lengthN=2^(n), where N denotes the codeword block-length. The generator matrixG_(N) may be defined by the Kronecker power of

${F = \begin{bmatrix}1 & 0 \\1 & 1\end{bmatrix}},$G _(N) =F ^(⊗n)  Equation 2

where ( )^(⊗n) stands for n-th Kronecker power of ( ). The generatormatrix may also be defined as G_(N)=B_(N)F^(⊗n), where B_(N) denotes thebit reversing matrix and it changes the order of elements in u₁^(N)=[u₁, u₂, . . . , u_(N)]. The bit reversing operation may be furtherdescribed herein. Without loss of generality, G_(N)=F^(⊗n) may beassumed unless noted otherwise as discussed herein.

Some input bits for polar code may have a fixed value (e.g., zero) andare called “frozen bits”. The input indexes for frozen bits may berepresented by the set A^(c)={a₁ ^(c), a₂ ^(c), a₃ ^(c), . . . , a_(N−K)^(c)} and a_(i) ^(c)<a_(j) ^(c) if i<j. The remaining part of input bitsfor polar code may convey variable information bits and are called“unfrozen bits”. The input indexes for unfrozen bits may be representedby the set A={a₁, a₂, a₃ . . . , a_(K)} and a_(i)<a_(j) if i<j. Thenumber of information bits, or unfrozen bits, may be defined as K andthe number of frozen bits may be N−K.

The code rate R of polar code may be defined as

$\frac{K}{N}.$

The determination process of input bit indexes for frozen bits andunfrozen bits is called “code construction” for polar code.

FIG. 2 is a diagram that illustrates an example polar encoder with thecode word block-length N=8. As shown, the polar encoder may berepresented by the nodes and the nodes are denoted by (i,j), i=1, . . ., N and j=0, . . . , n. As an example, consider the calculation of thevalue assigned to node (1,2) only. u₁ and u₂ are XOR'ed, which isassigned to node (1,1). u₃ and u₄ are XOR'ed, which is assigned to node(3,1). Then, the values of nodes (1,1) and (3,1) are XOR'ed, which isassigned to node (1,2). The values of the other nodes in FIG. 2 may besimilarly determined.

There may be several code construction methods for polar code. Ingeneral, the methods may initially calculate the reliability of eachinput bit index, and then have an order of bit index reliabilitiesbefore starting the encoding operation. From the obtained reliabilityorder, the least reliable input bits may be assigned as frozen bits andthe remaining bits may be assigned as unfrozen/information bits. Theproportion of frozen and unfrozen bits may be determined according tothe desired code rate. With the frozen and unfrozen bit locationsavailable, the encoding operation follows as in Eq. 1 and shown in theexample of FIG. 2.

Generally, decoding algorithms for polar code may be categorized intotwo types: Successive Cancellation (SC) based decoding, and BeliefPropagation (BP) based decoding.

SC polar decoding may be a sequential decoding method to calculate loglikelihood ratio (LLR) value of input bits in a serial manner; it isbased on the assumption that the previously decoded bits are correct andthey are used for decoding a current bit. Successive Cancellation List(SCL) decoding adopts several lists of candidate paths to improve theperformance of SC decoding, where the best list is selected according tothe outcome of the LLR calculation. Cyclic redundancy check (CRC) AidedSuccessive Cancellation List (CA-SCL) decoding adopts the embedded CRCas a tool to select the list. By CA-SCL decoding, polar code may achieveerror performance comparable or superior to conventional low-densityparity-check (LDPC) code or turbo code.

In some cases polar code may be decoded by a message passing algorithmcalled standard Belief Propagation (BP) based decoding or LDPC-like BPdecoding according to the sum product algorithm or min sum algorithm;this may be shown with a factor graph representation of polar code(e.g., FIG. 2). Message passing may be a powerful technique that may beused in various iterative based decoders, such as within LDPC decodersand neural networks.

BP based decoding (a.k.a., BP decoding) may be used in decoding ofvarious code-classes, including LDPC codes. As described herein, BPdecoding may be applied to polar codes. In an improved approach, denotedas LDPC-like decoding, BP decoding procedures may be modified based onthe features utilized in LDPC codes. Specifically, in the techniques ofLDPC-like decoding, the factor graph described above (e.g., FIG. 2) maybe pruned for a simpler and lower complexity configuration in order toadopt the LDPC decoding characteristics. Factor graph is a bipartitegraph and used in various iterative decoding methods, such as BPdecoding, although it should be noted that factor graph may also be usedfor encoding. The factor graph may comprise of two types of nodesdenoted as variable nodes and check nodes, respectively.

FIG. 3 is a diagram that illustrates an example of LLR message passingfor BP decoding. The metric (e.g., LLR values) calculations and theirrelationships between the nodes may be observed in FIG. 3. In FIG. 3, Lstands for left, and R stands for right, and i and j reference thediagram of FIG. 2. The equations of FIG. 3 are explained as follows:

L _(i,j) =L _(i,j+1) ,L _(i′,j+1) +R _(i′,j))  Equation 3

L _(i′,j) =G(R _(i,j) ,L _(i,j+1))+L _(i′,j+1)  Equation 4

R _(i,j+1) =G(R _(i,j) L _(i′,j+1) +R _(i′,j))  Equation 5

R _(i′,j+1) =G(R _(i,j) ,L _(i,j+1))+R _(i′,j)  Equation 6

Here, G(x, y)=sgn(x)sgn(y)min(|x|, |y|), and sgn(x) is a sign value ofx. When x≥0, sgn(x)=1 and when x<0, sgn(x)=−1. |x| is the absolute valueof x. The standard BP decoding algorithm by message passing shown may beperformed in an iterative manner. One iteration step may be divided intotwo half iteration steps. When round robin scheduling is assumed, thefirst half iteration may initially calculate metrics (e.g., LLR values)based on Eqs. 3 and 4, and starts from the rightmost nodes (codewordvariable nodes) and continues with the same metric calculations (Eqs. 3and 4), until it reaches the leftmost nodes (input bit nodes). Thesecond half iteration may perform metric (e.g., LLR values) calculationsbased on Eqs. 5 and 6 starting from the leftmost nodes until reachingthe rightmost nodes.

FIG. 4 is a diagram that illustrates an example method for orderedtransmission of polar code. Generally, a transmission procedure has atransmitter 410 start with a set of information bits provided by ahigher layer at 411. At 412, the set of information bits are polarencoded. At 413 the polar encoded bits are interleaved according totechniques further described herein. At 414 the interleaved bits arethen modulated (e.g., QPSK), at which point the resulting modulated bitsare ready for transmission. A reciprocal process for decoding may occurat the receiver 420 side. Initially, at 421 channel symbols arereceived. At 422, the symbols are then demodulated and an LLRcalculation is performed. At 423 deinterleaving is performed, thetechniques of which are further described herein. At 424, early startdecoding is performed.

At the encoder side (e.g., transmitter), initially the order of code bitgeneration may be identified based on a detailed component polar codeselection procedure 401, which is further explained in the example ofFIG. 7. The identified order of code bits may be used to create groupsof code bit indices, which provides interleaving parameters for groupedinterleaving operation at 402, which is further explained in the exampleof FIG. 8. At the decoder side (e.g., receiver), deinterleavingprocedures based on the designed interleaver parameters at the encoderfacilitate an early start of decoding of the received symbols. Theseprocedures may enable the receiver 420 to start its decoding based onpart of deinterleaved LLR values only, such as before the reception ofall symbols, which may result in a faster overall decoding operation.

FIG. 5 is four diagrams that illustrate an example of polar codedecomposition into four possible component polar codes. Encodingoperations on ordered code bits, such as at 412, may first involvedecomposition of polar code into multiple component codes. A componentpolar code may have the same polar code structure as in the originalpolar code, however with reduced block length. As shown in the exampleof FIG. 5, there is polar code decomposition into component polar codesin case of N=16 and N′=8, where N′ denotes the length of component polarcode.

Polar code diagrams 501 and 502 show component polar codes that containinput bits (e.g., input nodes) within their structure. Polar codediagrams 503 and 504 show component polar codes that contain the outputcoded bits (e.g., output nodes). Note, when N=N′, the component polarcode may be the overall polar code itself. Also, for N=N′·N″ (with N′and N″ having integer values), the overall polar code may be decomposedinto N/N′ component polar codes each with code length of N′ togetherwith N/N″ component polar codes each with code length of N″.

As described herein, the component codes may be selected within thefamily of 501 and 502 as a main example, such that the component codescontain the input bits/input nodes in their structures and operationsand any other configuration of component polar code with equal lengthmay be assumed without loss of generality.

In some cases, the order of code bit generation in component polar codemay be sequential. In such cases, n timing steps are required forencoding a code block with length N=2^(n); at each timing step, aspecific part of coded bits may be generated.

FIG. 6 shows three diagrams that illustrate sequential encoding stepsand coded bit generation at each timing step for a given component polarcode of length N′=8. As shown, the solid black (i.e., filled in circles)nodes may indicate the generation of code bits at each timing stage(e.g., 601, 602, and 603), and the dashed lines indicate XOR operationscorresponding to each step; in this example there are three steps orstages. The code bits c₇, c₈ are generated at timing step 601; the codebits c₅, c₆ are generated at timing step 602; and the coded bits c₁, c₂,c₃, c₄ are generated at timing step 603. Once a code bit is generated ata given encoding step, its value remains unchanged in the upcomingencoding steps. Following this example, the code bit generation stepsmay be expressed as follows: c_(N+1−2) _(t) to c_(N) bits are generateduntil timing step t=1, . . . , n, and c_(N+1−2) _(t) to c_(N−2) _(t−1)bits are generated at timing step t=2, . . . , n.

FIG. 7 is a flow chart that illustrates an example method of identifyinga code bit order based on component polar codes with length N′=2^(n′).At 701 the process starts as part of an overall transmission process. At702, N/N′ component codes with length N′ are selected. At 703, theencoding level is established, for example, starting with t=1. At 704,there may be polar encoding step t of each component code.

At 705, if the set of code bit indices generated at timing step t isdefined as T_(t), then the corresponding code bits may be grouped underthis set T_(t). Then, the grouped bits (e.g., sets) may be ordered inaccordance with their order of generation, which may be denoted as T₁,T₂, . . . , T_(n′), (N′=2^(n′)).

At 706, if t=n′ then the order determination process is over, and thetransmission process (e.g., see example FIG. 4) may continue. If no,then t is incremented at 707, and the process repeats at 704.

At the end of the process 708, the transmission may be performed basedon this grouping order such that the code bits are transmitted followingthe sequence of T₁, T₂, . . . , T_(n′), (N′=2^(n′)). In an example,using the notation in FIG. 2 (e.g., c_(m) is represented by index m),T₁={7,8}, T₂={5,6}, and T₃={1,2,3,4}. Hence, the order of transmissionmay follow the sequence T₁, T₂, T₃. Specifically, in this example, thecode bit sequence 7,8,5,6,1,2,3,4 (e.g., c₇, c₈, c₅, c₆, c₁, c₂, c₃, c₄)may represent an order of transmission. Further, within the set T_(t)the corresponding code bits may be generated during the same timingstep, and the order of transmission within this set may be arbitrary,such as T₃={1,2,3,4}→1,2,3,4→4,3,2,1→2,1,4,3, etc. Hence, the overalltransmit bit code sequence may be altered accordingly.

Moreover, the order of transmission may be reversed, bit reversed, orbit reversed of reversed (e.g., reverse a sequence (01,10,11) as(11,10,01), and then apply bit reversal to this reversed sequence whichwould be (00,01,10)). For example, by reversing, i

N′+1−i: T₁={2,1}; T₂={4,3}; T₃={8,7,6,5}.

By bit reversing, i=0xpqr . . . s+1, a bit reversing of i may be equalto 0xs . . . rqp+1 (where 0xpqr . . . s is the binary expression ofi−1). For example, the bit reversing of i is 0x011+1=0x100=4 wheni=7=0x111=0x110+1. By applying this reversing operation, the followingorders may be obtained: T₁={4,8}; T₂={2,6}; T₃={1,5,3,7}.

By applying another reversing operation on the bit reversing, thefollowing orders may be obtained: T₁={5,1}; T₂={7,3}, T₃={8,4,6,2}.

In a polar code that is composed of N/N′ component polar codes withlength N′, the order of transmission may similarly follow the order ofcode bit generation in each component polar code. That is, when T_(t)^(i) stands for the set of code bit indices generated at timing step tfor the i-th component code, the transmission order may be given by:

U _(i=1) ^(N/N′) T ₁ ^(i) ,U _(i=1) ^(N/N′) T ₂ ^(i) , . . . ,U _(i=1)^(N/N′) T _(N) ^(i),  Equation 7

Note that at 705, U_(i=1) ^(N/N′) T_(t) ^(i) denotes the union of setT_(t) ^(i) and the set contains indices of all elements of code bitsgenerated at timing step t for all N/N′ polar component codes withlength N′. For example, when N=16 and N′=8 and the component code typecorresponding to 501 and 502 is adopted, then U_(i=) ² T₁^(i)={7,8,15,16}; U_(i=1) ²T₂ ^(i)={5,6,13,14}; U_(i=1) ²T₃^(i)={1,2,3,4,9,10,11,12}. As shown in the example, the transmit codebit order may be identified based on component polar code.

Generally, there may be modifications to polar codes that result insimilar error performance and code construction procedures. For example,some modifications may include the removal of the bit reversinginterleaver, or reversing the order of the encoding stages (e.g.,corresponding to the vertical index j in FIG. 2). The orderedtransmission schemes discussed herein may be applied to these modifiedpolar code candidates in a straightforward manner.

FIG. 8 is a diagram that illustrates an example of ordered grouping andgroup interleaving. Following encoding, interleaving may be performedbased on the identified code bit order. The procedures disclosed herein(e.g., FIG. 7) may be considered a grouping of polar code bits accordingto an identified code bit generation order, where this order isdetermined based on the code bit generation in component polar codes.The polar code bits may be grouped based on the index of output nodes,in accordance with the selected component polar codes which are used todetermine the code bit order. See for example the encoded output codeblock 801 from code bit group 1 to code bit group N/N′ in FIG. 8. Thatis, the grouping of polar code bits corresponds to dividing the totalcode bit block of a standard order (e.g., c₁, c₂, . . . , c₁₆ in FIG. 5)into small code bits blocks each with length N′. In this case, each codebit group (code bit block) corresponds to each component code of type501 and 502 in FIG. 5.

From the code bits generated in the above paragraph, the ones thatcorrespond to the same encoding and code bit generation timing steps maybe selected and gathered in a new group, such as ordering at 804. The“new group” corresponds to U_(i=1) ^(N/N′) T_(t) ^(i). For example, thefirst “new group” contains the code bits that have the same vertical, orrow, index with the nodes generated at the first timing step of thecomponent polar codes (U_(i=1) ^(N/N′) T₁ ^(i)) and the last “new group”is gathered code bits that have the same vertical, or row, index withthe nodes generated at the last timing step of the component polar codes(U_(i=1) ^(N/N′) T_(n″) ^(i)).

To improve error performance in the burst error channel (e.g., fadingchannel), an interleaving operation may be necessary. For each orderedgroup, the code bits within the group may be interleaved by the groupinterleaver at 803. The group interleaver 803 may be a pseudo-randominterleaver or block interleaver.

The combination of ordering of the code bits, placing them under thegroups according to this ordering 804, and interleaving of the code bitgroups 803 as a whole may be considered interleaving over the total codebits 802. The interleaver processes, including ordering, creation ofcode bit groups, and group interleaving may be inserted in a NRmultiplexing chain as shown in FIG. 9, where the next step would be to amodulation mapper and/or a circular buffer (e.g., 805). N′ may be equalto the length of subblock used for subblock interleaver, which may beN′=32 in NR implementations.

As noted above, FIG. 9 is a flow chart that illustrates an example of aNR multiplexing chain modified with an interleaving stage 904 inserted.The process would otherwise include one or more of the followingelements/stages: polar encoding 901, subblock interleaver 902, bitselection 903, circular buffer 905, and modulation mapper 906.

Generally, a decoding operation may be performed with ordered code bitsjust as they were generated in an encoding operation as discussedherein. Belief propagation (BP) based decoding operations performed onordered code bits may enable an early start to the decoding process. BPbased decoding may be mostly performed in an iterative manner withmultiple iterations to complete the overall decoding operation. Inconventional polar decoding, the decoding may start when the LLR valuescorresponding to all code bits are prepared after reception of allchannel symbols. In comparison, for BP based decoding the decoder maybegin the decoding operation before receiving all channel symbols, whichmay allow for a faster response time.

FIG. 10 is a diagram that illustrates an example of timing relation inearly start decoding. In one code block interval, such as 1001 a, forthe TX there may be several ordered groups (e.g., ordered group 1,ordered group 2, and ordered group 3). Similarly, the RX 1020 mayreceive the same as what was transmitted from the TX 1010.

Based on the transmission procedures disclosed herein, the RX 1020 mayreceive the channel symbols according to the selected encoding andtransmission order from the TX 1010. In each reception of ordered codebit group(s), (e.g., for N′=8 and n′=3), and after calculation of LLRvalues from the received channel symbols, the decoder may selectdecoding procedure(s) for the code bit group(s) depending on itsdecoding method, such as low density parity code (LDPC)-like BP orstandard BP decoding. For example, decoding may be performed in oneiteration involving a half (right value) iteration plus a half (leftvalue) iteration. In another example, decoding may be performed in oneiteration involving half (variable to check) iteration plus half (checkto variable) iteration in an LDPC-like BP iteration. In another example,decoding may involve multiple iterations, where for each reception of anordered code bit group multiple iterations may be performed.

In BP decoding, each iteration may require 2n timing steps, and itfollows then that I iterations may require 2nI timing steps in total.The scaling factor “2” in 2n and 2nI depicts two half-iterationscorresponding to a left value calculation and a right value calculationas given in Eq. 3 to Eq. 6. For example, twelve (12=I) iterations mayrequire 2×10×12=240 timing steps for code length N=2¹⁰. On the otherhand, in LDPC-like BP decoding, only 2I timing steps may be required.Similarly, the scaling factor “2” in 2I depicts two half-iterationscorresponding to variable node to check node calculation (e.g., leftvalue calculation) and check node to variable node calculation (e.g.,right value calculation).

As shown in FIG. 10, the timing relationship between conventional startdecoding 1032 and early start decoding 1031 may be seen. If theiteration number is counted from the end of the code block reception anddoes not include the iterations from early decoding, the benefit ofearly start decoding may be evaluated. By adopting early start decoding,the decoder may finish its decoding process faster than the conventionalBP decoding and hence a faster response (e.g., ACK/NACK response to thetransmission) may be possible. It follows then this early decodingmethod may provide benefits for use cases, such as URLLC.

FIG. 11 is a flow chart illustrating an example decoding procedure.Initially at 1101, the decoding process begins as part of the processingrequired for receiving a transmission. At this point t=1 as seen at1102. At 1103, the ordered code bit groups (e.g., the “new groups” shownin the example of FIG. 9) that correspond to decoding step t arereceived. For each reception, at 1104 the decoder may calculate LLRvalues of channel symbols. At 1105, the corresponding nodes to thereceived group (the rightmost nodes in FIG. 2) may be initialized by theLLR values before decoding iteration(s). Once the LLRs are initialized,at 1106 decoding iteration(s) may be performed (e.g., early decoding),where the number of iterations may be a single (e.g., one) or multiplefor each decoding step as described herein. The nodes that correspond tothe code bit groups that have not been yet received are initialized tozero value. At 1108, t is assessed, and if t=n′ is not reached then t isincremented at 1107 and returns to the process. But if t=n′ is reachedand all decoding steps by early decoding are completed, at 1109 thenormal (conventional) decoding iterations as described above may beemployed further to finish all decoding procedure to have final decodedbits (e.g., by incorporating the additional decoding iterationsnecessary to complete the decoding of the full code block). The decodingiteration may be continued until the predetermined maximum iteration.Instead of stopping by the maximum iteration limit, conditions to stopdecoding early may be defined.

The length of component polar code N′ may be determined based on a fewconsiderations. The interleaving depth of the total interleaver 802 maybe closely related to the performance under a burst error channel (e.g.,fading channel). The adjacent code bits before interleaving may beseparated with a distance of d after interleaving when the internalinterleaving within the “new group” in FIG. 8 is done properly. Theseparated distance d may be larger than a specific value to overcome aburst error. N′ may be closely related to d because N′ is a basicseparation between different code bit groups (e.g., CC1, CC2, . . .etc.; see for example encoded output code block 801) and need to beselected in consideration of d.

In the case of orthogonal transmissions in a frequency domain, such asOFDM, the time difference between the transmitted signals may be verysmall which would limit the applicability of the early start of decodingprocedures. In order to provide a latency reduction benefit, the numberof time units in a single transmission interval (corresponding to apolar coded block) should be equal or larger than n′. Thus, n′ andcorresponding N′ may have upper bounds (e.g., “new group” corresponds toU_(i=1) ^(N/N′) T_(t) ^(i)), such as a predetermined/configuredthreshold.

Within the time interval corresponding to the transmission of one “newgroup” in FIG. 9, at least one decoding iteration should be performed tofacilitate the detailed early decoding procedures and benefit from thereduced latency. When n′ is too small and the corresponding timeinterval for decoding by single received group may be too short, thedecoder implementation may not perform even one iteration step. Thedecoder implementation capability to perform a single iteration may beone of factors that influence N′.

N′ may have a range of its values influenced by the above considerationsand may be determined to show the best error performance within therange. The error performance may be compared by simulation or realimplementation.

As discussed herein, the transmitter and receiver may be any twodevices, different or the same, as described herein, such as a WTRU. Inone case, the transmitter may be a network node and the receiver may bea WTRU for data transmission by polar encoding, or the transmitter maybe a WTRU and the network node may be the receiver. The receiver maysend a signal indicating the capability of its polar decoder in thesetup procedure of connection before the data transmission. Thetransmitter may decide the resource allocation indicating time intervalfor transmission and send the corresponding control information to thereceiver before the data transmission. The control information/packetmay be sent over any control channel (e.g., PDCCH) before a polar codeddata transmission. The control information may contain the informationindicating N′ implicitly based on predetermined rules or contain thisinformation explicitly. The receiver may need to decode the controlinformation/packet to obtain the polar encoding/decoding relatedinformation (e.g., N′). After the receiver receives the controlinformation, the transmitter may transmit the data based on the controlinformation. The receiver may have an early decoding procedure based onthe frame format indicated by the received control information.

In one example, a polar code may be initially divided into multiplepolar component codes. The features of these component codes (e.g., thenumber of component codes and/or the size of the component codes) may bedetermined based on parameters such as the number of available timingunits within a transmission interval, interleaving depth, and/or decodercapability. For each selected component code, the order of code bitgeneration and their indexes may be determined. The determined indexesmay then be assigned into different, unique groups according to theorder of code bit generation. An interleaving operation may beconfigured and then executed according to the determined index grouping.In the transmission phase, the code bits may be transmitted based on theidentified order of the bit generation in the component polar codes,such as determined index grouping. In a receiver, the decoder may startits decoding process of the received channel symbols utilizing the orderof the transmission information made available to itself (e.g., viapreviously transmitted control information), and therefore the decodingprocess may already start before all channel symbols are received.

In one example, a device, such as a WTRU or a network node, may performan operation for sending a packet that using polar encoding. Initially,the device may receive capability information from the receiver anddetermine time interval information based on the capability informationof the receiver. The device may send control information to the receiverso that the receiver will be able to decode a future packettransmission. The encoding process may begin with receiving data from ahigher layer for transmission. The data may be polar encoded. The devicemay then decompose the polar code into a plurality of component codes.The device may then group a code bit of a first component code with acode bit of a second component code based on a timing order of code bitgenerations by each component code, wherein the first component code andthe second component code are part of the plurality of component codes.The device may then interleave each group of code bits and out theinterleaved group(s) to a modulator which outputs a packet fortransmission. The packet is transmitted to a receiver, where it isdecoded based on control information received from the device prior tothe transmission of the packet. The total count of the plurality ofcomponent codes is based on one or more of a number of available timingunits within a transmission interval, an interleaving depth, and adecoder capability. The length of each of the plurality of componentcodes is based on one or more of a number of available timing unitswithin a transmission interval, an interleaving depth, and a decodercapability. The device may also determine an order of the code bits andindex(es) for each component code as part of the encoding process.

In one example, a polar code may be initially divided into multiplepolar component codes where the features of these component codes, suchas the number of component codes and the size of the component codes,are determined based on parameters such as the number of availabletiming units within a transmission interval, interleaving depth, anddecoder capability. For each selected component code, the order of codebit generation and their indexes may be determined. The determinedindexes may be assigned into different, unique groups according to theorder of code bit generation. An interleaving operation may beconfigured and then executed according to the determined index grouping.In the transmission phase, the code bits may be transmitted based on theidentified order of the bit generation in the component polar codes,such as the determined index grouping. In the receiver, the decoder maystart its decoding process of the received channel symbols utilizing theorder of the transmission information made available to itself a priori,and therefore the decoding process may star before receiving all channelsymbols.

Example conditions for performing simulations to illustrate theprospective advantages are provided in Table 1.

TABLE 1 Simulation Conditions Parameters Values N 1024 K  512 Code rate½ CRC No CRC Decoding scheme Flooding BP or LDPC like BP Codeconstruction NR polar code sequence Modulation QPSK Maximum iterationFlooding BP = 60, LDPC like BP = 300 Flooding BP Scaled min sum roundrobin (0.9375) Early decoding Block based early decoding N′ = 32Iterations for early Flooding BP = 1, LDPC like BP = 4 timing stepMinimum counted error 100 block errors

FIG. 12 is graph illustrating an example of a comparison of simulatedblock error performance between example procedures for conventional andearly start decoding. FIG. 13 is graph illustrating an example of acomparison of simulated timing steps between example procedures forconventional and early start BP decoding; likewise, FIG. 14 is graphillustrating an example of a comparison of simulated timing stepsbetween example procedures for conventional and early start LDPC-like BPdecoding.

For purposes of the present simulations, LDPC like BP decoding may bemodified based on polar decomposition. The length of component polarcode for early start decoding may be N′=32. One iteration may be assumedfor each early BP decoding of ordered group and four iterations may beassumed for each early LDPC like BP decoding of ordered group. In thesimulations, the component polar code with N′=32 may be used for orderedgroup selection and the cases of FIGS. 5 501 and 502 may also beassumed. The order of code bit generation by the encoding method basedon the sparse parity check matrix may be assumed, and may provide adifferent generation order of code bits from the encoder of aconventional NR approach.

From the results shown in FIG. 12, no performance difference betweenconventional decoding and early start decoding may be observed. From theresult of FIG. 13, 58.9% of iterations at SNR=4 dB may be reduced byearly start decoding but 44.6% of iterations may be increased at SNR=4dB by early start decoding. From the result of FIG. 14, 45.9% ofiterations at SNR=4 dB may be reduced by early start decoding but 14.2%of iterations at is increased at SNR=4 dB by early start decoding.

The disclosed operations in the encoder may result in modifying theorder of encoded bit streams, which may be identified by comparing suchbit-stream produced by the other encoding method of transmissions.Moreover, the details of operation employed for ordering of encoding maybe determined by investigating various test input (e.g., uncoded) bitstreams and their corresponding encoded bit stream outcomes.

Also, as detailed herein, the polar decoding operation may requiremodification based on the disclosed ordering operations. Therefore, inorder to allow inter-compatibility, the procedures in the ordering ofencoding may be disclosed and agreed-on, which may provide the relevantmodifications in the decoder.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element may be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

1. A method comprising: decomposing a polar code into a plurality ofcomponent codes; transmitting a packet, wherein the packet includes aninterleaved group of code bits, wherein the code bits were generated bygrouping a code bit of a first component code with a code bit of asecond component code based on a timing order of code bit generations ofeach component code, and wherein the first component code and the secondcomponent code are part of the plurality of component codes decomposedfrom the polar code.
 2. The method of claim 1, the interleaved group ismodulated.
 3. The method of claim 1, wherein a total count of theplurality of component codes is based on one or more of a number ofavailable timing units within a transmission interval, an interleavingdepth, and a decoder capability.
 4. The method of claim 1, wherein alength of each of the plurality of component codes is based on one ormore of a number of available timing units within a transmissioninterval, an interleaving depth, and a decoder capability.
 5. The methodof claim 1, further comprising determining an order of code bits andindex for each component code.
 6. The method of claim 1, furthercomprising: receiving capability information of the receiver;determining time interval information based on the capabilityinformation of the receiver; and sending control information to thereceiver prior to transmitting the packet.
 7. The method of claim 1,wherein the method is performed by a wireless transmit receive unit(WTRU).
 8. The method of claim 1, wherein the method is performed by anetwork node.
 9. A device comprising: a processor operatively coupled toa transceiver, the transceiver and processor configured to: decompose apolar code into a plurality of component codes; transmit a packet,wherein the packet includes an interleaved group of code bits, whereinthe code bits were generated by grouping a code bit of a first componentcode with a code bit of a second component code based on a timing orderof code bit generations of each component code, and wherein the firstcomponent code and the second component code are part of the pluralityof component codes decomposed from the polar code.
 10. The device ofclaim 9, wherein the interleaved group is outputted to a modulator. 11.The device of claim 9, wherein a total count of the plurality ofcomponent codes is based on one or more of a number of available timingunits within a transmission interval, an interleaving depth, and adecoder capability.
 12. The device of claim 9, wherein a length of eachof the plurality of component codes is based on one or more of a numberof available timing units within a transmission interval, aninterleaving depth, and a decoder capability.
 13. The device of claim 9,the processor further configured to determine an order of code bits andindex for each component code.
 14. The device of claim 9, the processorand transceiver further configured to: receive capability information ofthe receiver; determine time interval information based on thecapability information of the receiver; and send control information tothe receiver prior to transmitting the packet.
 15. The device of claim9, wherein the method is performed by a wireless transmit receive unit(WTRU).